The patients -- one woman and four men -- got their disc transplants in 2000 and 2001. They had had herniated discs in the neck.

Five years after the transplants, the patients had less disc pain than before surgery, and their immune systems hadn't rejected the transplanted discs, according to the doctors.

The technique needs refinement, but disc transplantation "could be an effective treatment for degenerative disc disease," the doctors write.

They include Keith D.K. Luk, FRCS, a professor in the University of Hong Kong's department of orthopedics and traumatology. The report appears in The Lancet.

Disc Transplant

Discs serve as pads, or shock absorbers, between the spine's bony vertebrae. Discs have a tough outer membrane and an elastic core.

A distorted, or herniated, disc can injure the spinal cord or the nerves connected to the spinal cord. Degenerative disc disease is the leading cause of herniated discs.

Luk's team studied spinal disc transplantation in primates for 12 years before performing the first human transplants in 2000 and 2001.

The human patients were 41-56 years old (average age: 47) when they underwent disc transplant surgery.

During the operation, they received spinal discs donated from young women who had recently died from trauma.

The disc recipients got thorough checkups, including X-rays and spinal scans using magnetic resonance imaging (MRI), in the years following their operation. The report in The Lancet covers the first five to six years of follow-up.

Spinal Results

Five to six years after disc transplant surgery, the patients' neurological symptoms were better than before their operation, and their immune systems hadn't rejected the transplanted discs.

Overall, the discs kept the patients' necks supple and stable, though the doctors report "mild" signs of degeneration in the transplanted discs five years or more after the operation.

The results are "promising" but longer follow-up is needed, states a Lancet editorial in the same issue.

"Nevertheless, the feasibility of the technique has now been shown," write the editorialists, including Jean Dubousset, MD, of the biomechanics lab at the Ecole National Superieure d'Arts et Metiers in Paris.

The Hong Kong study "could open a new dimension in the treatment of degenerative disc disease," write Dubousset and colleagues.

They note that current treatments for disc problems -- which include surgery -- sometimes don't totally relieve spinal pain and can limit the spine's range of motion.

Luk's team has already modified their technique in transplanting discs in a second series of patients. The results of those transplants aren't yet available.